12.2.1 Configuring and Using Kdump

During installation, you are given the option of enabling Kdump
and specifying the amount of memory to reserve for it. If you
prefer, you can enable kdump at a later time as described in
this section.

If the kexec-tools and
system-config-kdump packages are not already
installed on your system, use yum to install
them.

To enable Kdump by using the Kernel Dump Configuration GUI.

Enter the following command.

# system-config-kdump

The Kernel Dump Configuration GUI starts. If Kdump is
currently disabled, the green
Enable button is
selectable and the
Disable
button is greyed out.

Click Enable to enable
Kdump.

You can select the following settings tags to adjust the
configuration of Kdump.

Basic Settings

Allows you to specify the amount of memory to
reserve for Kdump. The default setting is 128 MB.

Target Settings

Allows you to specify the target location for the
vmcore dump file on a locally
accessible file system, to a raw disk device, or
to a remote directory using NFS or SSH over IPv4.
The default location is
/var/crash.

You cannot save a dump file on an eCryptfs file
system, on remote directories that are NFS mounted
on the rootfs file system, or
on remote directories that access require the use
of IPv6, SMB, CIFS, FCoE, wireless NICs,
multipathed storage, or iSCSI over software
initiators to access them.

Filtering Settings

Allows to select which type of data to include in
or exclude from the dump file. Selecting or
deselecting the options alters the value of the
argument that Kdump specifies to the
-d option of the core collector
program, makedumpfile.

Expert Settings

Allows you to choose which kernel to use, edit the
command line options that are passed to the kernel
and the core collector program, choose the default
action if the dump fails, and modify the options
to the core collector program,
makedumpfile.

For example, if Kdump fails to start, and the
following error appears in
/var/log/messages, set the
offset for the reserved memory to 48 MB or greater
in the command line options, for example
crashkernel=128M@48M:

kdump: No crashkernel parameter specified for running kernel

The Unbreakable Enterprise Kernel supports the use
of the crashkernel=auto setting
for UEK Release 3 Quarterly Update 1 and later. If
you use the crashkernel=auto
setting, the output of the
dmesg command shows
crashkernel=XM@0M, which is
normal. The setting actually reserves 128 MB plus
64 MB for each terabyte of physical memory.

Note

You cannot configure
crashkernel=auto for Xen or
for the UEK prior to UEK Release 3 Quarterly
Update 1. Only standard settings such as
crashkernel=128M@48M are
supported. For systems with more than 128 GB of
memory, the recommended setting is
crashkernel=512M@64M.

Click Help for more
information on these settings.

Click Apply to save
your changes. The GUI displays a popup message to remind
you that you must reboot the system for the changes to
take effect.